I'm about to go in on a job as a Data Wrangler and it's been long enough for me in between wrangling to lose touch with a reasonable estimate of calculating ROUGHLY what sizes of storage space I should be looking at considering the following:

I'm fighting to get a more exact idea but no one can get back to me with a shooting ratio, script length or any other idea aside from what I know above.

SO, I'd be keen to hear if there are any estimates out there from people with a better memory/ more experience than me.

otherwise, would appreciate if anyone could point me in the right direction of some resources that have a method for working out a vague calculation based on those bare essentials. Is there a rule of thumb?

You need a rough idea of what they expect to shoot, or you're nowhere. You could guess something, but you'd be on very thin ice unless you built in a truly massive safety factor, and even then you could find yourself working under Mr Seven Hours a Day and end up in serious trouble.

ProRes 4444 runs fractionally under 300Mbps, or a bit more than 130GB an hour. Beyond that, it's just multiplication. With a single LTO deck, assuming reasonable supporting gear, you could theoretically keep up with several hours a day, but you need some wiggle room.

It's the fourth item down from the top. I don't know how you can possibly be expected to estimate the daily byte count without a daily page count or expected shooting ratio.
Maybe the production company has produced a comparable show recently that you can use as a template?

Usually a script roughly works out at around a minute per page. However, on TV series, the scripts can be over length, script editors claim 5%, but it can be 10% to 15% over length according a film editor friend working on UK television dramas..

Well approximate shooting ratios are always going to be a more accurate way to plot out your data needs. However, without that, I'd work off the fact that on a single camera narrative shoot, when the cast and crew are on fire, and you're smashing out scenes - you might just get two hours of material recorded on a single day. So I'd plan around that two hours/day figure lacking better info.

Odds are you'll be over-catered for with that much space on most days, but better safe than sorry,